On Wed, 30 Jan 2008 16:25:12 -0600 (CST) Bruce Allen <[EMAIL PROTECTED]> wrote:
> Hi Stephen, > > Thanks for your helpful reply and especially for the literature pointers. > > >> Indeed, we are not asking to see 1000 Mb/s. We'd be happy to see 900 > >> Mb/s. > >> > >> Netperf is trasmitting a large buffer in MTU-sized packets (min 1500 > >> bytes). Since the acks are only about 60 bytes in size, they should be > >> around 4% of the total traffic. Hence we would not expect to see more > >> than 960 Mb/s. > > > Don't forget the network overhead: > > http://sd.wareonearth.com/~phil/net/overhead/ > > Max TCP Payload data rates over ethernet: > > (1500-40)/(38+1500) = 94.9285 % IPv4, minimal headers > > (1500-52)/(38+1500) = 94.1482 % IPv4, TCP timestamps > > Yes. If you look further down the page, you will see that with jumbo > frames (which we have also tried) on Gb/s ethernet the maximum throughput > is: > > (9000-20-20-12)/(9000+14+4+7+1+12)*1000000000/1000000 = 990.042 Mbps > > We are very far from this number -- averaging perhaps 600 or 700 Mbps. > That is the upper bound of performance on a standard PCI bus (32 bit). To go higher you need PCI-X or PCI-Express. Also make sure you are really getting 64-bit PCI, because I have seen some e1000 PCI-X boards that are only 32bit. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
